The present invention relates to an improved highway crash cushion that operates to decelerate an impacting vehicle safely and efficiently.
Highway crash cushions are widely used to decelerate impacting vehicles while limiting deceleration to safe levels for occupants of the vehicles. Such cushions are used alongside roadways in many applications, such as in front of bridge piers and other obstructions. Additionally, highway crash cushions are positioned on shadow vehicles such as heavy trucks that are parked in front of work zones. The truck protects the work zone against intrusion from a vehicle that has left the roadway, and the highway crash cushion protects the impacting vehicle and the shadow truck during the collision.
June U.S. Pat. No. 5,642,792, assigned to the assignee of the present invention, discloses one highway crash cushion that is mounted to a truck via a support frame that includes articulated arms. An energy absorbing element is disposed in the support frame, which is designed to collapse and to decelerate an impacting vehicle in a controlled manner.
The present invention is directed to an improved highway crash cushion and associated method that provide important advantages in terms of improved design flexibility. This allows the crash cushion designer to tailor the decelerating loads imposed by the crash cushion on the impacting vehicle to optimize efficiency. This invention is defined by the following claims, and nothing in this section should be taken as a limitation on those claims.
By way of introduction, the crash cushion described below includes a frame that forms at least first and second bays arranged one behind the other in an anticipated impact direction. The frame includes at least first, second and third transverse frames spaced from one another along the anticipated impact direction such that the first bay is between the first and second transverse frames and the second bay is between the second and third transverse frames. At least four side frames are included in the frame, with the first and second side frames extending between the first and second transverse frames on respective sides of the first bay, and the third and fourth side frames extending between the second and third transverse frames on respective sides of the second bay. Each of the side frames is outwardly bowed and includes first and second side frame elements that are coupled to the respective transverse frames, and a hinge coupled between the first and second side frame elements. At least one energy absorbing element is disposed in at least one of the bays, and at least two restraints are coupled to the side frames to resist movement of the hinges.
The energy absorbing elements can take many forms. In one preferred form the energy absorbing element includes tapered deformable sheet metal elements. Each sheet metal element defines a longitudinal axis extending between a smaller and a larger end, and the longitudinal axes are generally aligned with some of the smaller ends facing a first side of the energy absorbing element and others of the smaller ends facing a second side of the energy absorbing element, opposite the first side.
The crash cushion described in detail below is one example of a new type of crash cushion having a system response profile that provides an unusually efficient operation and stops an impacting vehicle in an unusually short distance while complying with controlling regulations. The system response profile of the disclosed crash cushion is characterized by an initial portion, an intermediate portion and a final portion. The decelerating force of the response profile during the final portion has an average value F; the decelerating force during the initial portion peaks at a value substantially greater than F; and the decelerating force during the intermediate portion falls to a value substantially less than F. This system response profile initially slows the vehicle markedly, then substantially reduces or eliminates decelerating forces on the vehicle, and finally provides a controlled decelerating force to stop the vehicle. In this way, the time and distance required initially to slow the impacting vehicle by a specified amount (such as 12 meters per second) is minimized, and the impacting vehicle quickly reaches the third portion of the profile, where the impacting vehicle is decelerated at a high average rate, up to about 20 G in many applications.
The drawings and detailed description disclose the preferred embodiments in greater detail, along with many of their advantages.